Before you start loading document exhibits, you need to create a case.
On your case list (the first screen you see after signing in), click Add New Case.
Fill in the case details. Fields marked with an asterisk (*) are required — Case Number, Plaintiff, and Internal Case / Matter Number. You can also add a Display Name, Defendant, Judge, and Notes, and click Click to customize under the exhibit sticker to set up your exhibit stamp.
Click Create Case and your new case appears in the list.
You control which users can access this case after it's created, from Manage Case — see the Manage user access to cases article.